After a 35-year tenure that saw him advance from loan officer to president and chief executive officer of the oldest, and currently eighth-largest, mutual bank in Massachusetts, Mark F. Welch will retire from Newburyport-based Institution for Savings July 1, 2010.

Welch, who will turn 60 next year, informed the bank’s trustees of his plans at the board’s monthly meeting earlier this week. The board accepted Welch’s decision and on his strong recommendation elected Michael J. Jones, current executive vice president, chief operating officer and chief financial officer, as Welch’s successor, according to a statement from the bank.

Welch is only the 15th president of the Institution for Savings in its 189-year history. His career at the Institution for Savings spans more than three decades.

Welch joined the bank in 1975 as the bank’s first-ever mortgage officer and went on to manage the lending department for nearly two decades. In 2001, he was promoted to executive vice president and chief operating officer, a position he held until March 2004, when he was elected president and chief executive officer by the bank’s board of trustees.